Method and apparatus for simultaneously depositing and observing materials on a target

ABSTRACT

A system for joining at least two beams of charged particles that includes directing a first beam along a first axis into a field. A second beam is directed along a second axis into the field. The first and second beams are turned, by interaction between the field and the first and second beams, into a third beam directed along a third axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/454,967, filed Jun. 15, 2006, which is a continuation of U.S. patentapplication Ser. No. 11/084,409, filed Mar. 17, 2005, which is acontinuation of U.S. patent application Ser. No. 10/842,899, filed May10, 2004, now U.S. Pat. No. 6,906,453, granted Jun. 14, 2005, which is acontinuation of U.S. patent application Ser. No. 10/429,067, filed May2, 2003, now U.S. Pat. No. 6,815,880, granted Nov. 9, 2004, which is acontinuation of U.S. patent application Ser. No. 09/608,908, filed Jun.30, 2000, now U.S. Pat. No. 6,522,056, granted Feb. 18, 2003, whichclaims the benefit of U.S. Provisional App. No. 60/142,147, filed Jul.2, 1999.

BACKGROUND OF THE INVENTION

One aspect of the present invention relates to a system fordepositing—e.g. “writing”—materials on a target while simultaneouslymonitoring—e.g. “reading”—the deposition process.

Beam Joining in a Magnetic Field

It is well known that passing beams of unfocussed charged particlesthrough a magnetic field causes the constituent particles to separateaccording to particle charge-to-mass ratio and/or velocity. This is thebasic principle of mass spectroscopy. A byproduct of the passage of sucha beam through a magnetic field is the introduction of uncorrectableresolution-limiting aberrations to any subsequent images in the beam.

Rempfer and Mauck in a paper entitled Correction of Chromatic Aberrationwith an Electron Mirror, Optik Vol 92, No 1, (1992), disclosed that animage could be passed through a cylindrical magnetic turning field(CMTF) without limiting resolution if a real image were formed at thecenter of the magnetic field. In other words, the beam incident on theCMTF is focused at its center and thus may be refocused by a lens backto a single image without loss of resolution. Such a geometry is notuseful for mass spectrometry because subsequent images in the beam arenot easily separated by ion mass as they are in a system where the ionspass through a magnetic field substantially collimated. In other words,a mass spectrometry system uses an unfocused beam incident on themagnetic field. Then the beam normally passes through a lens and isseparated into different ion masses.

FEI Company sells an XL800 Full Wafer Scanning Microscope which uses anion beam for eroding—“machining”—a surface, and an electron beam forprobing and monitoring the progress of erosion. The two beam-formingstructures are separate but physically proximate one another.

Chromatic And Spherical Aberration Correction

Just as light beams passed through optical lenses will experienceresolution-limiting spherical and chromatic aberrations, so beams ofcharged particles passed through electrostatic and electromagneticlenses also include these aberrations, due primarily to two factors:

1. spherical aberrations are due to the failure of a lens to focusparticles at different lateral distances from the axis thereof to thesame point longitudinally on the axis, i.e., for a converging lens andparticles incident upon the lens parallel to the axis, particles fartherfrom the axis are focused nearer the lens than particles closer to theaxis; and

2. chromatic aberration are due to the failure of a lens to focusparticles of different energies to the same point on the axis.

Chromatic and spherical aberration may also be introduced into electronoptical systems from the sources of the beams. Where energy aberrationbecomes significant, it can be reduced by passing the beam through anenergy filter at the expense of reduced beam current.

Henneberg, U.S. Pat. No. 2,161,466, teaches that the aberrations ofelectrostatic mirrors have the opposite sign from those of electrostaticand electromagnetic lenses, and that such mirrors could in principle beused to correct spherical and chromatic aberrations of lens systems andbeam sources. Rempfer and Mauck, Optik, 1992 discovered that incidentand reflected beams of charged particles could be separated if thesingle homogenous beam is focused upon and passed through the geometriccenter of a substantially cylindrically symmetrical magnetic field,where the field is located at an image plane of a particle beam lens. Inthat system, two lenses were used to relay an image between eachdeflecting field, and small magnetic beam deflection angles werenecessary in order to prevent magnetic field distortion effects.Unfortunately, such a system is complicated and the deflection anglesare small. Further, small deflection angles cause distortion in the beamexiting the magnet.

Hereinafter, the term “incident beam” refers to a beam of chargedparticles which is directed toward an element which modifies it in someway.

Hereinafter, the term “reflected beam” or “exiting beam” refers to abeam of charged particles which has been modified in some way byinteraction with some element.

Magnetic Deflection of 127 Degrees or 135 Degrees

Leboutet et al., U.S. Pat. No. 3,660,658, disclose a mass separatorusing a magnetic deflector system which deflects a charged particle beamat an angle of 90 degrees to its initial axis, and which also includes amagnetic deflector which deflects the beam at an angle of 127 degrees.The particle beam of Leboutet et al. passes through the turning magneticfield unfocussed. The Leboutet et al. device relies on the unfocussednature of the beam to perform the mass separation.

Rose et al., U.S. Pat. No. 4,760,261, disclose an electron energy filterwhich operates at a preferred angle of 115 degrees. The geometry of Roseet al. incorporates a triangular-shaped magnet. Like Leboutet et al.,Rose et al. depend upon separating all but those particles within anarrow selected energy range from a beam of particles having a widespectrum of energies. Such a device is effective only when usingunfocused beams.

Crewe, U.S. Pat. No. 5,336,891, discloses an aberration-free lens systemwhich includes both magnetic and electrostatic components to obtainaberration-free imaging. All examples disclosed by Crewe (FIGS. 3 a-3 i)show deflections only of 45 degrees, 90 degrees, and 180 degrees.

Rose et al., U.S. Pat. No. 5,449,914, disclose an energy filter in whichthe beam is deflected four time at angles of 135 degrees. Rose et al.relies on an unfocused beam to perform its functionality.

Electrostatic Mirror Used With Magnetic Deflector

Wada, U.S. Pat. No. 5,254,417, discloses a reflection mask for producingreflected electrons from the surface of a substrate in a desiredpattern. An electron beam is deflected by an electromagnetic field intoan electrostatic mirror, from which it is reflected back into the fieldand deflected to continue in its former direction. Wada does not focusits incident or its reflected particle beams at the geometric center ofthe respective magnetic deflecting fields.

Rose et al., U.S. Pat. No. 5,319,207, disclose an electron beam passingthrough magnetic deflection fields B1/B2, deflected 90 degrees into amirror, reflected back through the magnetic deflector, and deflected 90degrees onto the object to be scanned. The magnetic deflector taught byRose et al. is a complex device formed by a pair of circular magneticpoles having sufficient separation therebetween to allow one or morebeams of charged particles to pass therethrough. Rose et al. focus theirincident beam on the hypothetical diagonal symmetry plane 3 g ofdeflector 3, and their reflected beam on the hypothetical diagonalsymmetry plane 3 h.

Combination Of Electrostatic Mirror And Cylindrical Magnetic TurningField

Rose et al., U.S. Pat. No. 5,319,207, further disclose an electron beampassing through magnetic deflection fields B1/B2, deflected 90 degreesinto an electrostatic mirror, reflected back through a square magneticdeflector, and deflected 90 degrees onto the object to be scanned. Roseet al. focus their incident and reflected particle beams on hypotheticaldiagonal symmetry planes. Further, the deflector of Rose et al. issquare, and has two magnetic fields which must be adjusted and balancedfor strength.

What is desired, is a system for depositing—e.g. “writing”—materials ona target while simultaneously monitoring—e.g. “reading”—the depositionprocess.

BRIEF SUMMARY OF THE INVENTION

The present inventions, in several aspects, overcome the aforementioneddrawbacks of the prior art by providing a system for joining at leasttwo beams of charged particles that includes directing a first beamalong a first axis into a magnetic field. A second beam is directedalong a second axis into the magnetic field. The first and second beamsare turned, by interaction between the field and the first and secondbeams, into a third beam directed along a third axis.

In another aspect of the present invention a system separates at leasttwo beams of charged particles by directing a first beam along a firstaxis into a magnetic field where the first beam includes mixed chargedparticles. The first beam is directed at the magnetic field. The mixedcharged particles are separated into at least a second beam and a thirdbeam, by interaction between the magnetic field and the first beam.

In another aspect of the present invention a system turns at least twobeams of charged particles by directing a first beam along a first axisinto a magnetic field where the first beam exits the magnetic fieldalong a second axis. A second beam is directed along a third axis intothe magnetic field where the second beam exists the magnetic field alonga fourth axis. The third axis is at least one of colinear and coaxialwith the second axis and the second beam along the third axis has adifferent direction of travel than the first beam along the second axis.

In another aspect of the present invention a system focuses at least twobeams by providing a first beam and a second beam that are coaxial withone another where the charge of the first beam is opposite from thecharge of the second beam. The first beam and the second beam aredirected through a lens such that the first beam and the second beam arefocused at the same plane.

In another aspect of the present invention aberrations are reduced in abeam of charged particles by directing the beam along a first axis to amagnetic field where the beam leaves the magnetic field along a secondaxis that is not colinear with the first axis. The second axis isdirected toward a mirror. The beam is reflected from the mirror along athird axis. The beam is reflected from the mirror along a third axis.The beam is directed along the third axis to the magnetic field wherethe beam leaves the magnetic field along a fourth axis that is notcolinear with the first axis.

In another aspect of the present invention a system for depositingparticles on a target and monitoring the depositing includes providing afirst beam of ions, a second beam of electrons, and combining the firstbeam and the second beam into a coaxial third beam by interactionbetween the field and the first and second beams. The ions are depositedfrom the third beam on the target. The deposition is monitored with theelectrons of the third beam.

In another aspect of the present invention a system for depositing atleast one ionized atom on a target and moving the at least one atom intoa desired position include at least one ionized atom from a first sourcethat is directed to a magnetic field along a first axis, and toward thetarget along a second axis different from the first axis by interactionof the at least one ionized atom and the magnetic field. At least oneelectron from a second source is directed to the magnetic field along athird axis, and toward the target along a fourth axis by interaction ofthe at least one electron and the magnetic field. The at least oneionized atom is deposited on the target. The at least one electron isdirected in such a manner as to move the deposited at least one ionizedatom on the target to a desired position.

The foregoing and other objectives, features, and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention, taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIGS. 1A-1F diagrammatically represent different interactions of beamsof charged particles with a magnetic field.

FIG. 2A is a diagrammatic representation of the simplified geometry of amagnetic field and mirror.

FIG. 2B is a ray diagram of the paths of charged particles of FIG. 2A.

FIG. 2C is a ray diagram of the paths of charged particles in thegeometry of FIG. 2B for angles less than 127 degrees.

FIG. 2D is a ray diagram of the paths of charged particles in thegeometry of FIG. 2B for angles greater than 127 degrees.

FIG. 3 is a simplified diagrammatic representation of a system fordepositing ionic materials on a target and detecting with an electronbeam the deposited ionic materials.

FIG. 4 is a simplified diagrammatic representation of a relay lens forseparately deflecting “read” and “write” beams, as used in FIG. 3.

FIG. 5 is a simplified diagrammatic representation of the beamdeflectors used in FIGS. 3 and 4.

FIG. 6 discloses a compact spatial arrangement of two electrostaticlenses, a magnetic field, and a mirror.

FIG. 7 discloses an arrangement of a magnetic field for joining separatebeams of charged particles, and two lenses focusing beams on a target.

FIG. 8 represents an interaction of beams with an electrostatic ormagnetic field.

FIG. 9 represents a generic magnetic and/or electric field interactingwith multiple beams.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

In light optics the beamsplitter is an element used to combine orseparate beams. It may be a transparent substrate with one surfacepartially transmitting and partially reflecting. It may be placed in abeam of light at an angle to the beam so that the beam is separated intotwo parts. The coatings of the beamsplitter may be prepared so that thebeam is separated into different wavelengths, intensities, and/orpolarizations, as desired. The beam directions may likewise be referredto so that the separate beams are combined into a single coaxial beam.By analogy, in electron optics, there has not been a correspondingelement to the beamsplitter. Accordingly, charged particle opticalsystems requiring the joining or separating of beams along a commonaxis, are not realizable.

To illustrate the limitations due to aberrations which should be dealtwith for the preferred embodiment of the system of the present inventionto work most effectively, consider the effect of an electrostatic mirrorM on a beam of charged particles from object source S, which beam ispassed through objective lens L1, having a magnification factor m1, andthrough compensating lens L2, having a magnification factor m2, tomirror M. Both objective lens L1 and compensating lens L2 will introduceboth chromatic and spherical aberration to the image of source S on itsincident path as well as on its reflected path back through L2 to theimage plane of L1 from mirror M. Chromatic aberration is proportionateto the square of the product of m1, m2, and spherical aberration isproportionate to the fourth power of the product of m1, m2.Electrostatic mirror M will also introduce both chromatic and sphericalaberration into the reflected image of source S but they will be of theopposite sign from those introduced by L1 and L2. By choice of thecorrect parameters for mirror M and magnification factors m1 and m2,both aberrations of the mirror may be set equal and opposite to cancelthose aberrations introduced by L1 and L2. Consequently, the image ofsource S reflected back to the image plane of L1 by mirror M will besubstantially aberration-free. Further, the mirror parameters can beadjusted to present a substantially over-corrected image at L1 whichwill correct for aberrations of a lens system preceding or following L1.

To simplify illustrating and understanding the functionality of thedifferent aspects of the present invention, and in particular acylindrical magnetic field, for turning beams of electrified particles,FIGS. 1A-2D are for the purpose of illustrating several differentsituations of particular interest.

Particle beams entering and leaving electric, electrostatic, magnetic,or electromagnetic elements may be modified in some manner, all of whichare generically referred to herein as a field. Consequently, to moreclearly distinguish the entering beam from the exiting beam, theentering beam will be referred to as the “incident” beam and theexisting beam will be referred to as the “reflected”, “exiting”, or“leaving” beam.

In the following detailed discussions of the interaction of beams ofelectrically-charged particles with magnetic fields, beam E willrepresent an electron beam, and beam I will represent positive ornegative ion beams. The beams are preferably focused at the geometriccenter O of a cylindrically symmetrically uniform magnetic turning fieldF, and will appear to be emanating from the center O after havingtraversed field F. The field F may be substantially cylindrical,substantially symmetrical, and/or substantially uniform, as desired,through the remainder of the description herein. The beam may be focusedat substantially the geometric center O, as desired, through theremainder of the description herein. It is also to be understood thatany type, shape, field and/or charge distribution, of magnetic field maybe employed, as desired, through the remainder of the descriptionherein. It is further to be understood that the beam may be focused orunfocused and directed at the center or elsewhere, as desired, throughthe remainder of the description herein. Also, while many illustrationsshow only one or two beams, it is to be understood that any number ofbeams may be employed, as desired.

Some of the beams may be coaxial in nature, as desired. In addition, thebeams may be colinear in nature, as desired. Beams where the particlesare moving in the same direction are labeled as additive for convenienceof illustration, i.e., E1+E2, I+E, etc. Beams where the particles aremoving in the opposite directions are labeled as subtractive forconvenience of illustration, i.e., I−E, I1−I2, etc.

Coaxial or colinear beams of differing charge and/or direction of motionwill not affect one another to any measurable degree except forbeneficial space charge neutralization possible in intense beams.Investigations into the nature of sub-atomic particles use physicallymassive particle accelerators accelerating enormous currents ofcounter-rotating particles to nearly the velocity of light, yetcollisions between the particles are random and rare.

FIG. 1A illustrates the behavior of two charged particle beams E and Ias they pass through field F, the circumference of which is indicated byP. Beam E includes rays “A”, “B”, and “C”, the paths of which through Fare traced by “A”-“A”, “B”-“B”, and “C”-“C”, respectively. Beam Iincludes rays “A′”, “B′”, and “C′”, the paths of which through F aretraced by “A′”-“A”, “B′”-“B”, and “C′”-“C”, respectively.

Beams E and I are preferably focused at the center O and emerge fromfield F as a combined beam E+I containing both particles intermingledcoaxially, or colinearly, as desired. Combined beam E+I will appear tobe emanating from the center O of field F.

The particles of beam E are less massive and/or have lower velocity thanthose of beam I, as indicated by the greater angle through which beam Eis turned by field F, compared to the angle through which beam I isturned. In essence, FIG. 1A illustrates the joining of two oppositelycharged particle beams into a single beam.

FIG. 1B is a diagrammatic representation of incoming coaxial (orcolinear) beam E+I, which is preferably focused at the geometric centerO of magnetic field F. It is to be understood that the beam may befocused at other portions of the magnetic field, especially dependent onthe geometry of the magnetic field. Magnetic field F is preferablyoppositely directed from field F of FIG. 1A. The beam preferablyincludes mixed charged particles, such as for example, different chargeto mass ratio, different charges, and/or different energies.

The paths of rays “A”, “B”, and “C” of beam E are indicated by “A”-“A”,“B”-“B”, and “C”-“C”, respectively. The paths of rays “A”, “B”, “C” ofbeam I are indicated by “A”-“A′”, “B”-“B′”, and “C”-“C′”, respectively.The individual particles are separated according to well-known physicalprinciples as they pass through magnetic field F. In essence, FIG. 1Billustrates the separation of a mixed beam of oppositely chargedparticles into two distinct particle beams.

FIG. 1C is a diagrammatic representation of a beam E1−E2 of similarlycharged particles, such as electrons, traveling in different, such asopposite, directions. Magnetic field F is preferably oriented similarlyto that shown in FIG. 1B. Beam E1 is incoming from below and exits tothe left, above. Beam E2 is incoming from the right, above, and exitsbelow, with E1 but in the opposite direction. Preferably beam E1−E2 is acoaxial beam, but may also be colinear. Both beams are preferablyfocused at the center O as they enter magnetic field F, and both appearto be emanating from center O as they exit.

The paths of rays “A”, “B”, and “C” of beam E1 through field F, incomingfrom the bottom, are traced by “A”-“A”, “B”-“B”, and “C”-“C”,respectively. The paths of “A′”, “B′”, and “C′” through field F,incoming from the top right, are indicated by “A′”-“A”, “B′”-“B”, and“C′”-“C”, respectively. In essence, FIG. 1C illustrates the mixing ofthree beams.

FIG. 1E is a diagrammatic representation of a beam I1+I2 of chargedparticles having the same sign, with different charge-to-mass ratios,and/or different velocities. Beam I1+I2 enters from the bottom and, whenpassed through the turning field F, I1 particles are separated from I2particles because I1 particles are less massive or lower velocity thanI2 particles and therefore will be turned more sharply.

Beam I1+I2 includes rays “A”, “B”, and “C”. The paths of I1 throughfield F are traced by “A”-“A”, “B”-“B”, and “C”-“C”, respectively. Thepaths of I2 are traced by “A”-“A′”, “B”-“B′”, and “C”-“C′”,respectively. It is noted that by reversing the direction of the beams,FIGS. 1D and 1E illustrate the behavior of beam I1 and I2, and thedeflections are opposite thereto because the particle velocities isreversed. In essence, FIG. 1E illustrates the separation of one particlebeam including multiple similarly charged particle beams into separatebeams.

FIG. 1F is a diagrammatic representation of two beams I and E having thesame sign charge-to-mass ratios, but with different masses and travelingin opposite directions. Both joining and separating the two beams isaccomplished simultaneously. Beam I is incoming from the right above,and beam E is incoming from below magnetic field F, where I−E ispreferably coaxial (or colinear), with the particles moving in differentdirections.

Beam I−E includes rays “A”, “B”, and “C”. The paths of beam I throughfield F are traced “A”-“A”, “B”-“B”, and “C”-“C”, respectively, and thepaths of beam E through field F are traced “A”-“A′”, “B”-“B′”, and“C”-“C′”, respectively. In essence, FIG. 1F illustrates the mixing ofthree similarly charged particle beams.

In the following detailed discussions of the interaction of beams ofelectrically charged particles with magnetic field F, such as acylindrically uniform magnetic turning field, and electrostatic mirrorM, beam E particles are electrons, beam I particles are positivelycharged ions, and incident beams are preferably focused at the geometriccenter O of the turning field F. Beams exiting from the field F appearto be emanating from center O thereof, and beams reflected from mirror Mare preferably focused at the center O of field F.

FIG. 9 illustrates the interaction of a plurality of beams with ageneric field, such as a field that is electric and/or magnetic. Thedirection of the travel of the particles of the beams may be modified,as desired.

FIG. 8 illustrates the passage of a beam through a pair of fields, suchas magnetic fields, and a lens combination. The entering beam ispreferably focused at the geometric center of and turned by the magneticfield. The beam is incident upon a lens. The lens then focuses the beamwhich again is focused preferably at the geometric center of anothermagnetic field. The resulting beam is identical to the incident beam.The preferred angle of turning is 63.5 degrees (of substantially 63.5degrees) for a total of 127 degrees (or substantially 127 degrees).

FIG. 2A is an idealized diagrammatic representation of the interactionof incident beam Ei with magnetic field F and electrostatic mirror M.Mirror M may have any suitable surface, such as a flat planar surface ora concave surface, as shown, depending upon the amount of correctivespherical and chromatic aberration to be effected on incident beam Ei.Beam Ei, focused on the center O of magnetic field F, the effectiveperiphery of which is indicated by P, enters field F from the upperleft. Field F turns incident beam Ei to the right (as viewed along thedirection of the beam) into mirror M, from which it is reflected as beamEr and focused on geometric center O of field F.

It is noted that the incident beam Ei and reflected beam Er arepreferably coaxial and/or colinear between mirror M and field F, eventhough beam Ei−Er particles are moving in opposite directions.

Reflected beam Er is again turned to the right (as viewed along thedirection of Er particle movement) by field F, effectively separating itfrom incident beam Ei for further beam manipulation.

It is to be understood that the turning angle of the incident beam isequal to the turning angle of the reflected beam. This turning angle hasuseful optical effects upon the beam traversing the assembly.

FIG. 2B is an idealized detailed diagrammatic representation of theinteraction of incident beam E with magnetic field F and electrostaticmirror M. FIG. 2B and FIG. 2A both illustrate the inversion of the imagethat occurs when beam E is reflected from mirror M.

Three rays “A”, “B”, and “C” of incident beam Ei are shown as image Q ofan arrow which is focused on the geometric center O of magnetic field F.However, as the beam is turned to the right toward mirror M, the imagewill appear to emanate from the geometric center O of field F. As beamEi is reflected from mirror M (as beam Er), image Q will undergo aninversion and will be focused upon the center O of field F.

In FIG. 2B, it may be observed that the angle of first turning is 63.5degrees (or approximately), and the angle of second turning is again63.5 degrees (or approximately), making the apparent angle of turning,between incident beam Ei and reflected beam Er, 127 degrees (orapproximately). These angles provide the advantage that, only at theseangles, the primary rays from an extended image enter and exit from thefield F/mirror M structure parallel to the axes of the incident andreflected beams, respectively. Other angles limit the field of view ofthe whole optical system by diverting the ray bundles away from theaxis, thus preventing outer rays of the beam from passing throughsubsequent optical elements or systems. Use of these angles permitsundeflected beams focused at the center of field F to be deflected andpass there through with minimum beam distortion and no loss ofresolution. This feature is useful for independently deflecting theindividual beams prior to joining them into a single coaxial beam, asdescribed previously, so that the beams focused in the final image atthe target may be independently manipulated.

Consequently, with the mirror arrangement disclosed in FIG. 2B, incidentbeam Ei will appear to have been turned 127 degrees to the left bymagnetic field F, without image Q having been inverted in the process.One advantage of this arrangement is that mirror M can be adjusted tocorrect both the chromatic and the spherical aberrations caused bypassage through any focusing lenses before and/or after turning andreflection shown in FIG. 2B.

FIG. 2C illustrates a ray diagram of the paths of charged particles inthe geometry of FIG. 2B for turning angles less than 127 degrees. Hereray bundles are heading toward the beam axis.

FIG. 2D illustrates a ray diagram of the paths of charged particles inthe geometry of FIG. 2B for turning angles greater than 127 degrees.Here the ray bundles are diverging from the beam axis.

FIG. 3 is a simplified diagrammatic illustration disclosing thepreferred structure for a complete system for depositing, or “writing”,ionized molecular materials on a target, and for monitoring, or“reading”, the materials as they are deposited or written, respectively.The drawing, while simplified as far as voltage supplies, supportingstructures, controls, spatial, and angular relations, etc., disclosesthe individual components desired for the system.

For convenience of understanding, a beam will be described as turning tothe “right” or “left” when viewed along, and in the direction of, themovement of the beam particles.

Ion source 24 emits an ionized beam 26 a of the particular materials tobe deposited, the nature of which is determined by the ultimate functionto be performed. Ion source 24 may be a liquid metal ion source, ifdesired. Beam 26 a is collimated by a lens 28, and the particular ionsdesired are selected by a mass filter 30.

A lens 32 focuses beam 26 a on a mass-selecting aperture 34. The massfilter 30 and mass selecting aperture 34 may not be needed if the ionsource used is composed of a single atomic isomer. The remainder of beam26 a is focused by lens 36 producing, with the selected ions, a realimage of the source 24 at the a center 38 of a first magnetic turningfield 40. First turning field 40 turns the charged incident beam 26 a tothe left into a first electrostatic mirror 42. A first relay lens 44 maybe required to provide a magnified or demagnified image of the source 24for a mirror 40 to act upon.

For clarity of description, incident beam 26 a will be identified asreflected beam 26 b after reflection from the mirror 42, although likelyno substantive change in the beam 26 a has occurred, other than reversalof the real image and correction (or overcorrection) by the mirror 42 ofchromatic and spherical aberration caused by passage through lenses 28,32, 36, and 44.

The mirror 42 produces a real, but reversed, image of the source at thecenter 38 of the first turning field 40 (with or without the influenceof lens 44), by which the reflected beam 26 b is directed to the leftthrough collimating lens 46 into a beam deflector structure 48, ashereinafter described in greater detail in FIGS. 4 and 5. Deflected beam26 b is refocused at the geometric center 52 of second magneticelectromagnetic components, and their requirement for heavily regulatedand smoothed, high current power supplies requires significantly morespace and imposes significantly greater equipment and engineering coststhan do electrostatic components.

However, the use of electromagnetic lenses and deflectors does not avoidthe spirit or intent of the invention.

Reflected beam 26 b is focused upon a geometric center 38 of acylindrically symmetrical magnetic turning field 40. In turn, a lens 46collimates turned beam 26 b before it is passed through a beam deflector48, and is thereafter focused by a lens 50 upon a geometric center 52 ofa turning field 54. Turned and focused beam 26 b is directed toward adesired destination, e.g., target 62 of FIG. 3, which may be any type ofdevice such as an individual integrated circuit die, or a larger wafer.

The relay lens assembly 45 allows the beam 26 b to be focused at thegeometric centers 38 and 52 of both turning fields 40 and 54.

Second magnetic turning field 54 is a joining field, joining ion beam 26b to electron beam 66 b in the preferred embodiment, as explained ingreater detail later.

The beam 26 b is turned to the left as it passes through the secondfield 54, and directed through beam focusing lenses 56 and 58 having acommon aperture stop 60. Stop 60 and lenses 56 and 58 form a preferredcombined beam-focusing system 58, generally referred to as a telecentricstop, as hereinafter described in greater detail. The beam 26 b iscoaxially joined by beam 66 b, and directed and focused by lenses 56 and58 preferably perpendicularly to, e.g., target 62, where a desiredarrangement of ions is to be deposited.

The preferred embodiment of the present invention includes second beamforming and manipulating structure, for controlling, aligning,manipulating, and modifying, the electron beam 66. For clarity ofexplanation, reading beam 66 (known from FIGS. 1A-1F and 2A-2D as beamE) will be described as incident beam 66 a before being diverted intomirror 68, and as reflected beam 66 b after reflection therefrom.Incident beam 66 a is emitted by electron source 64 which is,preferably, a well-known point source, e.g., a field emission cathode ora thermionic field emitter. Beam 66 a is collimated and focused by lens70 to the geometric center 72 of third turning field 74, and turned tothe right into second electrostatic mirror 68, which may be concave forgreater correction of chromatic and spherical aberration. Reflected beam66 b is focused by the mirror 68 to the geometric center 72 of the thirdfield 74, and again turned to the right into preferred deflecting andfocusing assembly 76, which includes collimating lenses 78 and 80, anddeflecting plate structures 82, as hereinafter explained in greaterdetail in connection with FIGS. 4 and 5. The lens 78 is focused on thegeometric center 72 of the third turning field 74, and lens 80 isfocused on the geometric center 52 of the second turning field 54. Beam66 b is turned to the right by field 54, so that it is coaxial with ionbeam 26 b, and focused perpendicularly to, and incident on, target 62.

The geometry of turning fields 40, 54, and 74 preferably deflects beams26 a, 26 b and 66 a, 66 b through an angle of 63.5 degrees.

A reflected beam 66 b is focused upon a geometric center 72 of acylindrically symmetrical magnetic turning field 74. In turn, a lens 78collimates turned beam 66 b before it is passed through beam deflectors82, and is thereafter focused by a lens 80 upon the geometric center 52of the turning field 54. Turned and focused beam 66 b is coaxiallyjoined with the beam 26 b and directed toward a desired destination,e.g., target 62 of FIG. 3.

FIG. 4 discloses in greater detail the preferred embodiment of relaylens structures 45 and 76. Both structures are identical, but will bedescribed separately for clarity.

Relay lens 45 includes beam deflectors 48 therein. This enables beam 26b to be focused and manipulated independently from beam 66 b so thatmicroprecision positioning thereof on target 62 is possible to obtainthe performance described hereinbefore.

Reflected beam 26 b is focused upon geometric center 38 of cylindricallysymmetrical magnetic turning field 40. In turn, lens 46 collimatesturned beam 26 b before it is passed through beam deflectors 48, and isthereafter focused by lens 50 upon geometric center 52 of turning field54. Turned and focused beam 26 b is directed toward a desireddestination, e.g., target 62 of FIG. 3.

Reflected beam 66 b is focused upon geometric center 72 of cylindricallysymmetrical magnetic turning field 74. In turn, lens 78 collimatesturned beam 66 b before it is passed through beam deflectors 82, and isthereafter focused by lens 80 upon geometric center 52 of turning field54. Turned and focused beam 66 b is coaxially joined with beam 26 b anddirected toward a desired destination, e.g., target 62 of FIG. 3.

It will be seen by those skilled in the art that compound relay lensassembly 45 allows beam 26 b to be focused at the geometric centers 38and 52 of both turning fields 40 and 54, respectively, while beingcollimated as it passes through deflecting structure 45.

The relay lens assembly 76 allows beam 66 b to be focused at thegeometric centers 72 and 52 of both turning fields 74 and 54,respectively, while being collimated as it passes through deflectingstructure 82.

A combination of assemblies 45 and 76, sharing a common magnetic turningfield, permits charged particle beams to be joined coaxially whendesired to accomplish certain functions not possible otherwise, asdescribed elsewhere herein. It does not matter whether the beams havethe same or opposite charges, as disclosed in FIGS. 1A-1F, or aretraveling in the same or opposite directions, as disclosed in FIGS.1A-1F.

FIG. 4 discloses the location of beam deflectors 48 and 82 in thepreferred embodiment of relay lens structures 45 and 76, respectively,in which the beams 26 b and 66 b are collimated where beam deflection isnot required, assembly may be replaced with a simple lens having objectpoint at 38 and image point at 54. The preferred deflection geometry isillustrated in FIG. 4 where each magnetic field deflects the beamthrough 63.5 degrees for a total combined deflection of 127 degrees.

FIGS. 5A-5C discloses in greater detail beam deflectors 48 and 82 asshown in FIGS. 3 and 4. These structures are useful to separatelydeflect monitoring and depositing beams. As these deflectors areidentical, a single description will suffice for both. The descriptionwill switch between FIGS. 5A-5C, as necessary for clarity.

An insulating housing 82 (depicted in FIGS. 5A and 5B) holds two sets 84and 86 of four uniformly electrically resistive rectangular deflectionplates 88 a-88 d (depicted diagrammatically in FIGS. 5A-5C) spaced fromone another to form square or rectangular tunnel 92 (depicted in FIG.5A).

Plates 88 a-88 d are joined at the four corners thereof by electricallyconducting contacts 90 a-90 d, as depicted in FIGS. 5A and 5C. Eachcontact 90 a-90 d is joined along two faces thereof to two resistiveplates 88 a-88 d. As examples, contact 90 a is joined on one face byplate 88 a and on an adjacent face by plate 88 d, and plate 90 b isjoined on one face by plate 88 a and on an adjacent face by plate 88 b,etc. The structures formed by plates 88 a-88 d and contacts 90 a-90 dfrom square tunnel 92 as seen from either end thereof, as depicted inFIG. 5A.

The two sets of deflectors 84 and 86 are mounted end-to-end butelectrically separated. Electrical connections from the deflectors toappropriate controls and voltage sources can be made by existingtechniques well-known to those skilled in the art, as can theappropriate voltages necessary to produce uniform electric deflectionfields in tunnel 92 between the plates.

The foregoing described structure has several advantages, depending onthe particular structure implemented. A charged particle beam traversingthe deflector will experience an electric field of two-fold symmetry,which does not distort the beam or add aberrations to it. Further, thefield is linear at the edges of the plates, so it will be linear wherethe beam passes, and will result in linear beam deflection/volt, makingprecision beam control possible. Finally, resistive deflecting plateswill dissipate scattered electrons and ions which land on the plates,and the consequent absence of stray charges in the deflectionenvironment is necessary for reproducible results.

The voltages on plates 88 a-88 c can be arranged to keep the center oftunnel 92 at ground potential, simplifying control circuitry therefor,or any other desired potential. The resulting uniform electric field canbe used to produce substantially linear deflections in the chargedparticle beams. The two sets of plates can be used to fix the apparentcenter of beam deflection to any point needed.

Further, in addition to deflection voltages, voltages can be added tointroduce a quadrupole moment to the beam by making the average verticalelectrode potential more positive or more negative than the horizontaldeflection electrodes. This feature permits compensation for theso-called “deflection aberration” due to different parts of the beamtraversing the deflector at differing average voltages, and hencediffering velocities, resulting in a focusing of the beam in thedirection of deflection. This compensation would need to be achieved ina separate structure in other type deflectors.

When two or more charged particle beams are to be joined at some pointin the system, e.g., as described and disclosed hereinbefore inconnection with FIG. 3, beam deflectors should be located priorto—“upstream from”—the joining magnetic field, e.g. as described anddisclosed hereinbefore in connection with FIG. 4, if the separate beamsare to be deflected independently simultaneously.

FIG. 6 discloses arrangement 55, as seen hereinbefore, of symmetricallycylindrical magnetic turning field 54 joining two separate beams 26 band 66 b, of charged particles having different charge to mass ratios,and two separate electrostatic lenses 56 and 58, focusing the two beams26 b and 66 b into a coaxial beam 61 at a common point on target 62.

Three electrode, electrostatic lenses (also known as Einzel lenses),exemplified by lenses 56 and 58, will focus either electrons or ionswith either a positive or negative potential on center electrodes 57 and59, of lens 56 and 58, respectively. What has not been known heretoforeis that there is a unique voltage which can be placed on centerelectrode 57 and 59, of lens 56 and 58, respectively, which willsimultaneously focus negative electrons of one energy and positive ionsof another energy at the same point and in the same plane.

The preferred embodiment will focus an electron beam and an ion beam,simultaneously, with the same lens at the same time. Consequently, anyion species may be used with an electron beam, since all ion beams ofthe same energy are focused similarly. Further, the beams do not have tobe traveling through the lens in the same direction to obtain the sameresults, as explained hereinbefore.

Further, this mode of operation is not limited to unipotential lenses. Asubstantial range of accelerating or decelerating electrostatic lensesexhibits the same properties. All unipotential lenses, accelerating ordecelerating, may be composed of any number of electrodes or electrodeshapes. This feature also permits the use of compound lenses to be usedwith a telecentric stop as shown in FIG. 6.

For example, the optical system of FIG. 6 is composed of twoelectrostatic lenses each having the characteristic of focusing twodifferent charged particle beams having different charge-to-mass ratiosand different energies. Unipotential lenses 56 and 58 willsimultaneously image beam 26 b of 15 kV electrons and beam 66 b of 5 kVpositive gallium ions apparently emanating from the geometric center 52of magnetic field 54, and join them in a common coaxial beam 26 b+66 bthrough telecentric aperture stop 60. To obtain identical lens strengthsfor both beams, a negative voltage beam 26 b-66 b through telecentricaperture stop 60. To obtain identical lens strengths for both beams, anegative voltage of −10.5 kV, applied to center electrode 57 and 59 oflens 56 and 58, respectively, will produce equal strengths for thepositive and negative components of coaxial beam 26 b+66 b. This voltageis about 70% of 26 b voltage −15 kv and about −210% of 66 b voltage. Thelens acts in the so-called accelerating mode for the ions, and in thedecelerating mode for the electrons, to produce the same lens strengthfor the two components of coaxial beam 26 b+66 b ( an electrostatic lensis generally weaker in the accelerating mode than in the deceleratingmode).

Lens 58 receives the combined coaxial collimated beam 26 b+66 b fromstop 60 and produces a simultaneous and coincident image of ion beam 26b and electron beam 66 b on the target plane 62. If stop 60 is placed inthe focal plane of lens 58, the optical system of FIG. 6 is capable ofproviding independent control of electron beam 66 b and ion beam 26 bwhich are perpendicular (or substantially perpendicular) to the targetplane 62 when it is desirable to scan the beams. An appropriatedeflection optical geometry, such as disclosed in FIG. 4, should be usedto avoid other troublesome aberrations.

A further use of this structure can be made by combining it with acylindrically symmetrical magnetic joining field, such a disclosed inFIG. 1A. Since the magnet turns a charged particle beam through an angleproportional to the square root of the charge-to-mass ratio, there isthe possibility of joining not only two beams with opposite signcharge-to-mass ratios, but also two or more charge-to-mass ratios withthe same sign charge-to-mass ratios. Coincident beams of differentcharge-to-mass ratios but same sign charge-to-mass ratios will befocused similarly by any subsequent electrostatic lens as long as theenergy of the beams is the same. Two or more joining magnets may becascaded to provide a plurality of ions to the target plane. This may beuseful in the deposition of alloys where simultaneous deposition ofmultiple elements is desired.

Even further, cylindrical joining magnets may be used to combine bothpositive and negative ions in a single beam, which may be important inthe construction of insulators and certain chemicals.

It is noted that the charged particles emanating from the target may bevaried. For example the particles may be the reflected beam and/orparticles, secondary electrons, secondary ions, etc.

Use can be made of both (1) the lens simultaneously passing and focusingin both directions and (2) the simultaneous joining and separatingability of the cylindrical magnet. Ions may be placed on a surface whilean electron beam is simultaneously probing the process. Both electronsand ions expelled from the work pass back through the lens and magnetand are separated, allowing individual detection of the returningspecies. This is helpful for aligning, monitoring, and manipulating ofindividual atoms or molecules, and in analytical analysis.

FIG. 7 discloses an arrangement of two electrostatic lenses X and Y,cylindrically symmetrical magnetic turning field Z, and electrostaticmirror M, in which the angles are 90 degrees. The separate axes of X, Y,and M pass through the geometric center O of turning field Z, and thebeam passing through all three optical elements X, Y, and Z is alsofocused at the geometric center O, making it possible to produce thesystem of FIG. 3 in a small physical space. Mirror M is shaped andbiased to have external focal point O, and to cancel the spherical andchromatic aberrations introduced into beam 26 b+66 b by lenses X and Y,as well as by any other lenses in the system, by introducingovercorrecting spherical and chromatic aberrations of opposite signthereto into the beam. Because only one magnetic turning field Z isinvolved, all axes lie in a common plane, lending its use to a moreeconomical and compact physical structure than that of FIG. 3. Thepreferred angle is 90 degrees, but other angles may likewise beemployed, as desired.

Suggestion has been made herein before that work of molecular and atomicdimension would be possible under the appropriate circumstances. Thefollowing facts give some idea of the possible dimensional resolutionspossible.

With both ion and electron beams completely corrected for spherical andchromatic aberration, an electron beam energy of two kilovolts (2 kV)gives an electron wavelength of 0.27 angstroms (A). The theoreticalresolution limit for such an electron beam in an aberration-correctedelectron optical system would be 1.67 A for an angular aperture of 100milliradians (mrad), and 16.7 A for 10 mrad angular aperture. Publishedresults of experiments conducted earlier by the present inventorcompletely corrected an electron beam from a 35 mrad angular aperture,and unpublished results of later experiments indicate completecorrection of a 100 mrad beam could be achieved under certaincircumstances. A beam of 8 kV electrons would give resolutions ofone-half these numbers.

Ions have a much shorter wavelength than electrons making atomicresolution possible with smaller beam energies, e.g., 330 eV galliumions have a wavelength of 0.002 A, and the corresponding resolutionwould be 0.12 A for a beam from a 10 mrad angular aperture. Ions from abeam of 300 eV and below have a reasonable probability of adhering to atarget, e.g., a substrate, giving a resolution of 0.1 the dimension ofthe smallest atom, and making possible subatomic placement of ions, andthe building of so-called “designer” molecules.

One potential use of the apparatus of the present invention is thedepositing of a single atom (such as an ion) on a substrate, and themoving into position of that atom—“nudging”—by a stream of electrons,while simultaneously observing the process.

Another use of the apparatus of the present invention is the use of anion beam to “sputter off” the surface of a compound to chemically mapthe surface thereof.

More specifically, referring to FIG. 3, the focusing and deflectingfunctions disclosed herein theoretically make it possible to placemolecular-sized, or even simple ion deposits with ion beam 26 a, 26 b,and simultaneously to scan, or read, with electron beam 66 a, 66 b whatis being deposited thereon.

Further, an electron beam could be used to erode the molecular-sizeddeposits into desired shapes, and/or to obtain the single ion deposits.

The correction of chromatic and spherical aberration in writing andreading beams, permits a reduction in size of individual integratedsemiconductor devices by several orders of magnitude, and a consequentsubstantial increase in density and/or speed of integrated circuits.

In the field of “nano-electronics”, one of the obstacles to research anddevelopment and, consequently progress therein, has been the lack ofmanufacturing processes and tools to investigate the physics of smalldevices. The system diagrammatically depicted in FIG. 3, and describedin connection therewith, could be used to fabricate“nanometer-dimension” electronic circuits directly from constituentmaterials. Conductor runs could be directly deposited without the aid oflithographs. Insulators could be grown in place only where they wereneeded, from a layer of silicon deposited on a substrate, andsubsequently converted to oxide with the aid of an oxygen ion beam.Direct “doping” could be performed in place by either “driving” ions inplace directly, or by first depositing them on the desired surface and“driving”, or melting, them with a directed electron beam. A substantialimprovement in semiconductor electronic production could be achieved bythe virtual elimination of toxic waste byproducts, since only materialsneeded to layout the circuits or devices would be deposited in thedisposition process described herein. Little or no etching ordissolving, with their toxic waste byproducts, would be generated.

All manufacturing of such devices and materials could be done withoutremoving the work from the system. Once a circuit was completed,connections could be made to power and test instrument terminalsfabricated in the system and the circuit could be evaluated in place.Imaging of the circuit in a diagnostic mode during testing could beperformed by e.g., scanning with a low energy electron beam or an ionbeam in a “mirror” mode. Modifications of the circuit could be made withion beams in place. When final circuit performance and configuration wassatisfactorily obtained, it could be reproduced automatically andindefinitely by a “step-and-repeat” process.

A significant obstacle to nano device investigation and manufacturing isthe alignment from one step in a process to the next. By simultaneouslyreading and writing along a coaxial optical axis these limitations areovercome. An indefinite array of structures may be “stitched” togetherwith sub-atomic precision.

Automatic fabrication of an endless variety of devices would be possiblewith the simultaneous “read/write” system disclosed in FIG. 3 anddescribed in connection therewith. Alignment and registration could becontrolled automatically, permitting the system to manufacture devicesof unlimited size and complexity by joining the “fields” together.Fields of interest which already exist for molecular-sized devices arebiology, medicine, mechanics, ecology, chemistry, physics, andelectronics.

It is not often realized that, as the size of devices is reduced beyonda certain point, serial production of some devices becomes not onlyfeasible but economically desirable when compared to parallelproduction. Liquid metal and gas-field ion sources are extremely bright,and provide more than sufficient current to build nanodeviceseconomically if the beams from these sources can be corrected forspherical and chromatic aberration as disclosed herein.

In addition to providing improved resolution, the preferred embodiment,by permitting aberration-corrected beams to be manipulated, alsoincreases the angular size of the beams to be increased, providingincreased beam current and throughput. This feature is of use inimproving speed and resolution of existing instruments such as scanningelectron microscopes, transmission electron microscopes, photo emissionmicroscopes, low energy emission microscopes, and other analyticalinstruments. Further, optical lithography mask-making and repair wouldbe benefitted thereby.

The terms and expressions which have been employed in the foregoingspecification are used therein as terms of description and not oflimitation, and there is no intention, in the use of such terms andexpressions, of excluding equivalents of the features shown anddescribed or portions thereof, it being recognized that the scope of theinvention is defined and limited only by the claims which follow.

1. A method for directing at least two beams of particles, comprising:(a) directing a first beam of particles along a first axis into a fieldwhere said first beam exits said field along a second axis; and (b)directing a second beam of particles along a third axis into said fieldwhere said second beam exits said field along a fourth axis, said thirdaxis is at least one of colinear and coaxial with said second axis andsaid second beam along said third axis has a different direction oftravel than said first beam along said second axis.
 2. The method ofclaim 1 wherein said field is a magnetic field having a geometric centerthereto.
 3. The method of claim 2 wherein said first beam is focusedupon said geometric center.
 4. The method of claim 3 wherein said secondbeam is focused upon said geometric center.
 5. The method of claim 4wherein said first and fourth axes are not coaxial.
 6. The method ofclaim 5 wherein said first and fourth axes are not colinear.
 7. Themethod of claim 1 wherein said second and third axes are coaxial.
 8. Themethod of claim 1 wherein said second and third axes are colinear. 9.The method of claim 1 wherein said field is a cylindrical magneticfield.
 10. The method of claim 1 wherein said field is a magnetic fieldhaving a substantially symmetrical cylindrical form having a geometriccenter thereto upon which said beams are focused.
 11. An apparatus thatco-axially directs at least two beams of charged particles, comprising:(a) a field; (b) a first beam of particles directed along a first axisinto said field; (c) a second beam of particles directed along a secondaxis into said field; and (d) whereby said first and second beams areco-axially aligned, by interaction between said field and said first andsecond beams, into a third beam directed along a third axis.
 12. Theapparatus of claim 11 wherein said field is a magnetic field having ageometric center thereto.
 13. The apparatus of claim 12 wherein saidfirst beam is focused upon said geometric center.
 14. The apparatus ofclaim 13 wherein said second beam is focused upon said geometric center.15. The apparatus of claim 14 wherein said third beam is at least one ofcolinear and coaxial.
 16. The apparatus of claim 15 wherein saidmagnetic field is cylindrical.
 17. The apparatus of claim 11 whereinsaid field is a magnetic field having a substantially symmetricalcylindrical form having a geometric center thereto upon which said beamsare focused.